/*
 * Copyright (c) 2007-2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package com.sun.org.apache.bcel.internal.generic;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import com.sun.org.apache.bcel.internal.classfile.Utility;
import java.util.HashSet;
import java.util.Collection;
import java.util.HashMap;

/**
 * Instances of this class give users a handle to the instructions contained in
 * an InstructionList. Instruction objects may be used more than once within a
 * list, this is useful because it saves memory and may be much faster.
 *
 * Within an InstructionList an InstructionHandle object is wrapped
 * around all instructions, i.e., it implements a cell in a
 * doubly-linked list. From the outside only the next and the
 * previous instruction (handle) are accessible. One
 * can traverse the list via an Enumeration returned by
 * InstructionList.elements().
 *
 * @author  <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 * @see Instruction
 * @see BranchHandle
 * @see InstructionList
 */
public class InstructionHandle implements java.io.Serializable {
    InstructionHandle next, prev; // Will be set from the outside
    Instruction instruction;
    protected int i_position = -1; // byte code offset of instruction
    private HashSet targeters;
    private HashMap attributes;

    public final InstructionHandle getNext() {
        return next;
    }

    public final InstructionHandle getPrev() {
        return prev;
    }

    public final Instruction getInstruction() {
        return instruction;
    }

    /**
     * Replace current instruction contained in this handle.
     * Old instruction is disposed using Instruction.dispose().
     */
    public void setInstruction(Instruction i) { // Overridden in BranchHandle
        if (i == null)
            throw new ClassGenException("Assigning null to handle");

        if ((this.getClass() != BranchHandle.class) && (i instanceof BranchInstruction))
            throw new ClassGenException("Assigning branch instruction " + i + " to plain handle");

        if (instruction != null)
            instruction.dispose();

        instruction = i;
    }

    /**
     * Temporarily swap the current instruction, without disturbing
     * anything. Meant to be used by a debugger, implementing
     * breakpoints. Current instruction is returned.
     */
    public Instruction swapInstruction(Instruction i) {
        Instruction oldInstruction = instruction;
        instruction = i;
        return oldInstruction;
    }

    /*private*/protected InstructionHandle(Instruction i) {
        setInstruction(i);
    }

    private static InstructionHandle ih_list = null; // List of reusable handles

    /** Factory method.
     */
    static final InstructionHandle getInstructionHandle(Instruction i) {
        if (ih_list == null)
            return new InstructionHandle(i);
        else {
            InstructionHandle ih = ih_list;
            ih_list = ih.next;

            ih.setInstruction(i);

            return ih;
        }
    }

    /**
     * Called by InstructionList.setPositions when setting the position for every
     * instruction. In the presence of variable length instructions `setPositions()'
     * performs multiple passes over the instruction list to calculate the
     * correct (byte) positions and offsets by calling this function.
     *
     * @param offset additional offset caused by preceding (variable length) instructions
     * @param max_offset the maximum offset that may be caused by these instructions
     * @return additional offset caused by possible change of this instruction's length
     */
    protected int updatePosition(int offset, int max_offset) {
        i_position += offset;
        return 0;
    }

    /** @return the position, i.e., the byte code offset of the contained
     * instruction. This is accurate only after
     * InstructionList.setPositions() has been called.
     */
    public int getPosition() {
        return i_position;
    }

    /** Set the position, i.e., the byte code offset of the contained
     * instruction.
     */
    void setPosition(int pos) {
        i_position = pos;
    }

    /** Overridden in BranchHandle
     */
    protected void addHandle() {
        next = ih_list;
        ih_list = this;
    }

    /**
     * Delete contents, i.e., remove user access and make handle reusable.
     */
    void dispose() {
        next = prev = null;
        instruction.dispose();
        instruction = null;
        i_position = -1;
        attributes = null;
        removeAllTargeters();
        addHandle();
    }

    /** Remove all targeters, if any.
     */
    public void removeAllTargeters() {
        if (targeters != null)
            targeters.clear();
    }

    /**
     * Denote this handle isn't referenced anymore by t.
     */
    public void removeTargeter(InstructionTargeter t) {
        targeters.remove(t);
    }

    /**
     * Denote this handle is being referenced by t.
     */
    public void addTargeter(InstructionTargeter t) {
        if (targeters == null)
            targeters = new HashSet();

        //if(!targeters.contains(t))
        targeters.add(t);
    }

    public boolean hasTargeters() {
        return (targeters != null) && (targeters.size() > 0);
    }

    /**
     * @return null, if there are no targeters
     */
    public InstructionTargeter[] getTargeters() {
        if (!hasTargeters())
            return null;

        InstructionTargeter[] t = new InstructionTargeter[targeters.size()];
        targeters.toArray(t);
        return t;
    }

    /** @return a (verbose) string representation of the contained instruction.
     */
    public String toString(boolean verbose) {
        return Utility.format(i_position, 4, false, ' ') + ": " + instruction.toString(verbose);
    }

    /** @return a string representation of the contained instruction.
     */
    public String toString() {
        return toString(true);
    }

    /** Add an attribute to an instruction handle.
     *
     * @param key the key object to store/retrieve the attribute
     * @param attr the attribute to associate with this handle
     */
    public void addAttribute(Object key, Object attr) {
        if (attributes == null)
            attributes = new HashMap(3);

        attributes.put(key, attr);
    }

    /** Delete an attribute of an instruction handle.
     *
     * @param key the key object to retrieve the attribute
     */
    public void removeAttribute(Object key) {
        if (attributes != null)
            attributes.remove(key);
    }

    /** Get attribute of an instruction handle.
     *
     * @param key the key object to store/retrieve the attribute
     */
    public Object getAttribute(Object key) {
        if (attributes != null)
            return attributes.get(key);

        return null;
    }

    /** @return all attributes associated with this handle
     */
    public Collection getAttributes() {
        return attributes.values();
    }

    /** Convenience method, simply calls accept() on the contained instruction.
     *
     * @param v Visitor object
     */
    public void accept(Visitor v) {
        instruction.accept(v);
    }
}
